Heating system using otherwise wasted heat and method of use

ABSTRACT

A flexible heat exchanger is incorporated into a ridge vent to form an assembly. The heat exchanger operates by collecting thermal energy (heat) from heated air exhausting from the attic space via the ridge vent. Air in the attic space is typically heated by the solar energy falling on the roof. Heat from this air is transferred through the wall of heat exchange tubes integrated into the ridge vent. The flow of heated air around the outside of the tubes is driven by the column of heated air that forms in the attic space, similar to the draft in a chimney. The chimney effect in the attic space circulates the flow of outside air into the soffit vents through the attic space where it is heated and then exhausted out the ridge vent, passing by and around the tubes before it exits.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No. 12/012,072 filed Feb. 1, 2008, which claims the benefit of U.S. Provisional Patent Application Nos. 60/921,863 and 60/921,867, both filed Apr. 5, 2007. The present disclosure relates to roof vents generally and more particularly to an energy recovery system in beneficial combination with a roof vent.

BACKGROUND

Structures incorporating sloped roofs typically include an attic space immediately beneath the roof rafters and above the occupied portions of the structure. The ceiling of the occupied portions of the structure, corresponding to the floor of the attic space, is typically insulated to thermally isolate the rest of the structure from what can be extreme temperature fluctuations in the attic space. The attic space is typically provided with ventilation designed to prevent the accumulation of heat and moisture in the attic space.

Various forms of attic ventilation are well known. Roof ridge vents are commonly used to cover an opening formed along the peak of a sloped roof during construction of the structure. The roof ridge vent takes the form of an elongated slot between the structural elements of the roof. Various forms of vent covers are attached to the roof structure surrounding the vent opening and are configured to allow air to leave the attic space, while preventing moisture, insects and the like from entering. Complementary vents are typically formed under the eaves of the roof and may be referred to as soffit vents. This combination of soffit and ridge vents work in combination with solar heating of the roof structure to establish a natural convective circulation of heated air entering at the soffit vents and exiting the roof structure at the ridge vent. Depending upon the time of year, geographic location of the structure (latitude), and ambient temperature, air within the attic structure can reach temperatures exceeding 160° F. Attic ventilation is typically arranged to limit accumulation of heat in the attic space and therefore limit transfer of unwanted heat from the attic space to the occupied portions of the structure.

It is known to use of the reservoir of heated air in an attic space as an energy source. Previous efforts to extract energy from the heated air beneath a roof structure have typically required the installation of complicated and expensive equipment in the attic such as disclosed in U.S. Pat. No. 5,014,770, which also includes a useful summary of other prior art arrangements used to extract energy from the air space beneath a roof structure. Some of the prior art requires assembly of large heat exchange apparatus in the attic space, such as that disclosed in U.S. Pat. No. 4,671,253.

An objective of the present disclosure is to provide a cost-effective system for recovering a portion of the energy represented by heated attic air exiting through attic vents.

Another objective of the present disclosure is to provide heat exchangers and roof ridge vents including a heat exchanger that recovery useful energy from the air space beneath a roof structure without requiring installation of equipment in the attic space or extensive modification of the roof structure.

SUMMARY

A flexible heat exchanger is incorporated into a ridge vent to form an assembly. The heat exchanger operates by collecting thermal energy (heat) from heated air exhausting from the attic space via the ridge vent. Air in the attic space is typically heated by the solar energy falling on the roof. Heat from this air is transferred through the wall of heat exchange tubes integrated into the ridge vent. The flow of heated air around the outside of the tubes is driven by the column of heated air that forms in the attic space, similar to the draft in a chimney. The chimney effect in the attic space circulates the flow of outside air into the soffit vents through the attic space where it is heated and then exhausted out the ridge vent, passing by and around the tubes before it exits. This chimney effect requires a warmer temperature inside the attic than the ambient outside temperature, which is typically the case during daylight and into the evening hours. The heat transfer coefficient outside the tubes, created by the velocity of the air flowing around the tubes, is the limiting thermal resistance to heat flow in the process of transferring heat to the fluid inside the tubes, assuming that the velocity inside the tubes is sufficiently high—typically at or above 3 feet per second.

The disclosed ridge vent heat exchanger assembly is manufactured in long flexible coils so that it can be rolled lengthwise during manufacture for storage and transport and unrolled to cover elongated openings such as roof ridge vent openings and capped in a conventional manner with shingles. Lateral side portions are configured from open, air permeable material such as mesh or thermoformed plastic materials. The lateral side portions serve two functions. First, they provide support to the cap of shingles. Second, they provide an elongated, air permeable vent for the exit of heated air from beneath the roof. The lateral side portions also include screen or fine mesh material to prevent the entry of insects or opportunistic animals. The lateral side portions are separated by an open central region having a width similar to that of the underlying opening along the roof ridge. The plurality of heat exchange tubes are suspended in the open central portion and exposed to the flow of heated air exiting through the vent opening.

According to one aspect of the disclosure, the flexible roof ridge vent material may be provided with a plurality of longitudinally spaced hangers constructed to support the heat exchange tubing. The hangers include receptacles configured to receive and support each of the plurality of heat exchange tubes. Each set of hangers may extend downwardly from a bracket extending laterally across the roof ridge vent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial sectional perspective view of a first embodiment of a heat exchange assembly according to aspects of the disclosure;

FIG. 2, is a sectional view of a roof structure incorporating the heat exchange assembly of FIG. 1;

FIG. 3 is a partial sectional perspective view of a second embodiment of a heat exchanger according to aspects of the present invention;

FIG. 4 is a sectional view of a roof structure incorporating the heat exchange assembly of FIG. 3;

FIG. 5 is a sectional view of an alternative roof structure incorporating the heat exchange assembly of FIG. 3;

FIG. 6 is a schematic of an energy recovery system incorporating a heat exchanger according to the present disclosure;

FIG. 7 is a partial sectional perspective view of a ridge vent heat exchanger assembly according to aspects of the present disclosure;

FIG. 8 is a partial sectional perspective view of a second ridge vent heat exchanger assembly according to aspects of the present disclosure;

FIG. 9 is a partial sectional perspective view of a third ridge vent heat exchanger assembly according to aspects of the present disclosure;

FIG. 10 is a perspective view of a bracket compatible with the disclosed heat exchangers and ridge vents;

FIG. 11 is a sectional view of the bracket of FIG. 10 incorporated into a ridge vent heat exchanger assembly according to the present disclosure;

FIG. 12 illustrates a residential structure incorporating a ridge vent heat exchanger assembly and energy recovery system according to aspects of the present disclosure;

FIG. 13 is a top plan view of an alternative heat exchanger assembly according to the present disclosure;

FIG. 14 is a partial sectional view through an embodiment of the lateral side portion of a roof ridge vent where the material is corrugated;

FIG. 15 is a partial top view of an embodiment of the lateral side portion of a roof ridge vent where the top sheet of the roof ridge vent is formed into a plurality of spaced apart protrusions defining air flow paths therebetween; and

FIG. 16 is a partial sectional view of the lateral side portion illustrated in FIG. 15, taken along line 16-16 thereof.

DETAILED DESCRIPTION

Reference should now be made to the drawing figures, provided for purposes of illustration and not limitation, in which common reference numerals refer to similar features of the enclosed embodiments. The figures illustrate various embodiments of elongated, flexible heat exchange assemblies and such assemblies integrated with elongated roof ridge vents. The disclosed heat exchange assemblies and roof ridge vents are configured to support a plurality of heat exchange tubes directly in the flow of heated air exiting through a roof ridge vent.

FIG. 1 illustrates a heat exchange assembly constructed according to aspects of the disclosure, and generally indicated by the reference numeral 10. Heat exchange assembly 10 includes an elongated flexible support 20 constructed of air permeable material embedded in which are a plurality of heat exchange tubes 22. FIG. 1 illustrates a heat exchange assembly including four longitudinally extending heat exchange tubes 22 arranged in a substantially parallel, equally spaced pattern. Other numbers of heat exchange tubes 22 and other spatial arrangements are compatible with the disclosure.

U-shaped connectors 24 join the four heat exchange tubes into a serpentine flow path having a length at least approximately four times the length of the heat exchange assembly 10. Such an elongated flow path extends the time the heat collecting fluid (working fluid) is in the heat exchange tubes 22, which are in contact with the heated air. Such an arrangement increases the quantity of energy extracted from the attic space. Heat exchange tubes 22 are preferably relatively narrow diameter to enhance the surface area of the heat exchange tubes relative to the volume of working fluid inside the tubes. One preferred heat exchange tube is approximately ½″ in outside diameter and formed from PEX, a cross-linked polyethylene, or other suitable material compatible with the liquid being handled. The working fluid used with the disclosed heat exchange assemblies is typically water or a water/ethylene glycol (anti-freeze) solution.

The heat exchange tubes 22 are arranged to occupy a central portion 21 of the support 20, with lateral portions 23 of the support 20 extending along either side of the central portion 21. The heat exchange assembly 10 is preferably manufactured by a continuous process and cut into lengths compatible with various standard residential or industrial structures. The support 20 and heat exchange tubes are preferably constructed of plastic selected to be flexible enough that the heat exchange assembly 10 can be rolled lengthwise into a spiral roll during manufacture and bundled in this form for storage and transport. The spiral roll of heat exchange assembly 10 can be unrolled during installation on a structure.

In the embodiment of FIG. 1, the heat exchange tubes 22 are embedded in the support 20, which is a porous, air permeable material. Roof ridge vent material 20 is porous and intentionally configured to permit attic air to exit the attic space through a ridge vent. Suitable materials include mesh or various thermoformed, extruded, or melt-blown plastic materials.

FIG. 2 illustrates the heat exchange assembly 10 of FIG. 1 installed over a roof ridge opening 30 on a roof 32. The heat exchange assembly 10 is covered with shingles 40 to form a cap that sheds precipitated moisture laterally onto the roof 32. The porous, air permeable support 20 prevents the entry of insects, rodents, birds or the like. It will be noted that the lateral portions 23 of the support 20 overlap with the roof structure on either side of the roof ridge opening 30 and provide a location for attaching the heat exchange assembly to the roof 32. The central portion 21 of the support 20 is configured to laterally span the roof ridge opening 30. The air flow path is generally vertical through the roof ridge opening 30 into the support 20 and then laterally through the air permeable support 20, exiting along the longitudinal sides of the heat exchange assembly 10 beneath the shingles 40 forming the cap. The support 20 is configured to maintain the heat exchange tubes 22 in a position directly in the path of heated air leaving the roof structure through the vent opening 30. The presently disclosed embodiments are compatible with any ventilation opening communicating with a space where the opening is configured to permit the release of heated air by convection.

FIG. 3 illustrates an alternative heat exchange assembly 10′ including four heat exchange tubes 22′ incorporated into an elongated support 20′. The heat exchange assembly 10′ of FIG. 3 dispenses with the lateral side portions 23 as shown in FIG. 1, but is otherwise similar in construction, materials and function to the heat exchange assembly 10 illustrated in FIG. 1. Connectors 24 join the heat exchange tubes 22′ into a serpentine flow path several times the length of the heat exchange assembly 10′. FIG. 4 illustrates heat exchange assembly 10′ installed in a roof ridge vent opening 30 in an alternative structural configuration to that illustrated in FIG. 2. In FIG. 4, the heat exchange assembly 10′ is installed within the roof ridge opening 30 and secured to the roof rafters 25. Shingles 40 cover the heat exchange assembly 10′ to shed precipitation onto the roof 32. Air exiting the roof ridge vent opening 30 flows vertically into the air permeable support 20′, past the heat exchange tubes 22′ and then laterally outwardly through the longitudinal sides of the support 20′ beneath the shingles 40 forming the cap. It will be noted that the flow area along the longitudinal sides of the arrangement illustrated in FIG. 4 is substantially smaller than the corresponding flow area of the arrangement illustrated in FIG. 2. This will typically result in reduced air flow through the vent opening, with a corresponding reduction in heat transfer to the heat exchange tubes.

FIG. 5 illustrates alternative heat exchanger 10′ installed beneath the peak of an attic roof or other space where recovery of waste heat is desired. Although the heat exchanger 10′ may be installed in any number of conventional ways, FIG. 5 illustrates the assembly held in position by a series of clamping members 120 held by means of fasteners 130, which may be nails or screws. The installation of FIG. 5 will be significantly less efficient in collecting heat from the attic space than the installation shown in either FIG. 2 or 4. The installations of FIGS. 2 and 4 position the heat exchange tubes 22, 22′ directly in contact with the flow of heated air exiting through a roof ridge vent opening 30, while the air in the installation of FIG. 5 will not typically have much movement. It is well known that fluid movement (flow) enhances thermal transfer by the process of convection. Convection can be natural or artificially produced by a motor driven fan or the like. In the case of the present disclosure, the various disclosed heat exchange assemblies and roof ridge vents are configured to benefit from the natural convection current in a roof structure where cool, dense air enters at the soffit vent and as it is warmed beneath the roof, expands and rises to exit through the roof ridge vent. Heat exchange installations exposed to less air flow will have less energy recovery capacity than those exposed to greater air flow.

The disclosed heat exchange assemblies are designed to be integrated into an energy recovery system configured to use the heat energy collected at the roof ridge vent for other purposes. FIG. 6 illustrates an energy recovery system 50, into which the disclosed heat exchange assemblies 10, 10′ may be incorporated. System 50 includes a pump 60 arranged to circulate working fluid in a fluid flow loop from a heat exchanger 10, 10′ in a roof structure and a heat exchanger 62 typically located in an energy accumulator such as an insulated hot water tank. Working fluid such as a water/propylene glycol solution is circulated between the heat exchanger 10, 10′ and a second heat exchanger 62 in a closed-loop. Alternative arrangements include those where tap water is fed through a heat exchanger located in an attic space and then delivered to a hot water heater. The working fluid will typically be water or water/antifreeze solution, but can be any other liquid compatible with system materials and the purpose of heat transfer. FIG. 6 illustrates an energy recovery system 50 in which the working fluid which has absorbed heat in the roof mounted heat exchanger 10, 10′ is circulated through heat exchanger 62 to deliver heat to a second liquid, such as domestic water. Heat exchanger 62 is typically situated in an insulated tank filled with facility domestic water. Heat recovered from the attic space by the heat exchanger 10, 10′ is delivered to the facility domestic water in the tank. Pre-heated water is thus delivered to the facility hot water generating equipment. Heat recovered according to the disclosed heat exchanger embodiments reduces the energy required to raise the domestic water temperature to the desired hot water temperature. Other heat storage media may be compatible with the disclosed heat exchangers and energy recovery systems.

Alternative embodiments of roof ridge vent assemblies incorporating heat exchangers according to aspects of the present disclosure are shown in FIGS. 7-9. In these embodiments, heat exchange tubes 22 are not embedded in porous roof ridge vent material, but are instead situated in an open central portion 21 between the lateral side portions 23. This configuration provides the most efficient interface between the heated air and the heat exchange tubes by limiting turbulence and thermal resistance at the interface of the heated air and heat exchange tubes 22. In these embodiments, air flow over the heat exchange tubes 22 tends to be laminar or smooth, rather than turbulent which would be the case if the heat exchange tubes were surrounded by the porous support material.

FIG. 7 illustrates an embodiment of a roof ridge vent 10 which includes a heat exchanger according to aspects of the disclosure. The roof ridge vent 10 includes a longitudinally extending top sheet 44 which may be solid or porous and is preferably constructed of a flexible plastic material. The central portion 21 of the roof ridge vent 10 is flanked by much thicker lateral side portions 23 constructed so as to permit relatively free air flow through the lateral side portions 23. The lateral side portions 23 may be constructed of air permeable porous material, corrugated material as shown in FIG. 14, or constructed in the form of a plurality of spaced apart protrusions as shown in FIGS. 15 and 16. Plastic material is preferred for the lateral side portions because of its low cost, durability and the variety of ways in which plastic material may be formed and handled. Whatever the construction, the lateral side portions 23 must permit air flow laterally away from the central portion 21. An air permeable scrim or sheet of mesh, screen or filter material 46 is applied along the bottom and longitudinal outside surfaces of the lateral side portions 23 to prevent ingress of wind-driven precipitation, insects, birds, rodents or the like. The lateral side portions 23 define the height of the roof ridge vent 10, which is typically less than one inch. The lateral side portions 23 have sufficient strength to receive fasteners to attach the roof ridge vent 10 to the roof structure and to support the cap shingles. The top sheet 44 has sufficient flexibility to conform to the roof structure as illustrated in FIG. 2. The angle formed between the roof portions on either side of the roof ridge vent opening varies according to the pitch of the roof, which is typically between 4 and 16 inches of height per foot of horizontal spread. The materials of the roof ridge vent and the size and spacing of the heat exchange tubes are selected to ensure that the lateral side portions will conform to the shape of the roof structure, while the heat exchange tubes are maintained in a spaced apart configuration to permit air flow around the tubes.

The lateral side portions 23 flank the open central portion 21 of the roof ridge vent 10. In the disclosed embodiments, longitudinally spaced rows of receptacles 48 are configured to receive and hold the heat exchange tubes 22 in pre-determined positions with respect to each other and to the roof ridge vent 10. The receptacles 48 illustrated in FIG. 7 are configured to elastically deform to receive and retain the heat exchange tubes 22. Other forms of receptacle are illustrated in FIGS. 8 and 9, which in all other respects are roof ridge vents similar to the roof ridge vent of FIG. 7. FIG. 8 illustrates receptacles 52 having ratchet-type U-shaped fasteners which support the heat exchange tubes 22. FIG. 9 illustrates simple J-shaped receptacles 54 for supporting the heat exchange tubes 22.

The rows of receptacles may be integrally molded with a laterally extending plastic bracket 56 such as illustrated in FIGS. 10, 11 and 13. The bracket 56 includes a central portion 57 for supporting the heat exchange tubes 22 in spaced apart relationship and lateral side extensions 58 for attachment to the lateral side portions of the roof ridge vent 10 as shown in FIG. 11. The brackets 56 may be attached to the roof ridge vent 10 by adhesive, heat bonding, stapling or any fastening technique. The heat exchange tubes 22 are secured to the central portion in a generally parallel, spaced-apart configuration by J-shaped receptacles 54. Flexible retaining posts 55 are longitudinally offset relative to the J-shaped receptacles 54. The J-shaped receptacles 54 and retaining posts 55 are configured to deflect when a heat exchange tube is inserted between the open end of the J-shaped receptacle 54 and the retaining post 55. Once the heat exchange tube 22 is received in the J-shaped receptacle 54, the plastic bracket material returns to its previous configuration where the receptacle supports the heat exchange tube 22 from below, while the retaining post 55 prevents the heat exchange tube 22 from leaving the receptacle. The receptacles and retaining posts also maintain the lateral spacing of the heat exchange tubes, even when the bracket 56 is flexed to conform to the shape of a roof structure. It should be noted that the heat exchange tubes 22 are also spaced apart from the top sheet 44 of the roof ridge vent 10, allowing air to circulate around the entire circumference of the tubes 22 as the air flows through the roof ridge vent 10.

Conventional roof ridge vent openings are typically between three and six inches in their transverse dimension, although other dimensions are possible and compatible with the disclosed embodiments. The disclosed roof ridge vent heat exchanger embodiments position a plurality of heat exchange tubes 22 in a spaced apart, generally parallel configuration and positioned between the laterally opposed air flow paths defined by the lateral side portions 23 of the roof ridge vent 10. In this configuration, air heated in the space beneath the roof flows by convection past the heat exchange tubes 22 as it passes through the ridge vent. This convective flow of heated air over the heat exchange tubes 22 facilitates heat transfer into the working fluid within.

Generally speaking, the greater the height of the space defined by the roof, the greater the speed of the convective flow through the ridge vent. This is known as a “chimney effect.” Faster flow of heated air across the heat exchange tubes generally provides greater heat transfer into the working fluid, permitting a greater rate of working fluid flow through the heat exchanger. U-shaped connectors 24 are employed to connect the heat exchange tubes into one or more serpentine flow paths extending the length of the roof ridge vent 10. The heat exchange tubes 22 employed in the disclosed embodiments are approximately one-half inch (0.5″) in outside diameter (OD) and three-eighths of an inch (0.375″) in inside diameter (ID). The flow rate at which working fluid is circulated through the heat exchangers is calculated to maximize heat transfer while minimizing energy consumed in circulating the working fluid. Typically, this flow rate will be in the range of two to five gallons per minute (2-5 gpm). Ideally, conduits through which working fluid is delivered to the attic and retrieved to the energy storage heat exchanger 62 are insulated to retain heat recovered from the attic.

Heat exchange tubes 22 may be conventional cylindrical tubes extruded from commonly used materials such as PVC or cross-linked polyethylene (PEX). Alternatively, heat exchange tubes 22 may be provided with enhanced heat transfer capability by addition of carbon fiber or other heat-conductive materials. The cross-sectional shape of the heat exchange tubes may be enhanced to further improve heat transfer. Vanes or fins may be employed on the inside surface of the heat exchange tubes 22 to modify flow of the working fluid and further enhance heat exchange. The vanes or fins may be located throughout the heat exchange tubes or located in the U-shaped connecting sections.

The brackets 56 and receptacles 54 will typically be configured so the heat exchange tubes 22 do not extend beyond the thickness of the lateral side portions 23 of the ridge vent 10, which could interfere with rolling and installation of the ridge vent. An alternative embodiment may employ flexible connectors such as tie-wraps to fix the heat exchange tubing to the hangers or protrusions descending from the top sheet.

In an alternative embodiment, the heat exchange tubes may be fixed to the central portion of the ridge vent during manufacture and without the use of brackets and hangers as a separate component. The central portion of the top sheet may be configured to include a plurality of downwardly extending protrusions where a connection with the heat exchange tubes 22 can be formed. The connection between the protrusions and the heat exchange tubes 22 may be formed by heat welding, adhesive or other conventional means compatible with the manufacturing process. The ridge vent heat exchange assembly 10 is cut to standard lengths for use in construction and rolled longitudinally into a spiral roll for storage and transportation.

At the job site, the ridge vent heat exchange assembly 10 is unrolled and secured spanning the ridge vent opening of a structure with the heat exchange tubes 22 exposed to the interior of the roof structure. U-shaped connectors 24 are employed to connect the longitudinal ends of the heat exchange tubes into one or more serpentine flow paths. Installation of the roof ridge vent heat exchange assembly 10 is essentially without cost, because the heat exchange assembly is integrated into a convenient to use and conventional roof ridge vent. Installation of the connectors and working fluid supply lines can be accomplished very inexpensively with push-on Sharkbite-type fittings.

The roof ridge vent heat exchange assembly 10 is then connected to a storage heat exchange assembly 62 positioned in a water tank 64 as shown in FIG. 12. Temperature sensors T1 and T2 detect the temperature in the attic space or the temperature of the working fluid in the heat exchanger 10, and storage tank, respectively. Thermostatically controlled switches are used to activate a circulating pump 60 to circulate the working fluid between the roof-mounted heat exchanger 10 which absorbs heat from the roof space and the storage heat exchanger 62 which transfers heat to water in the storage tank 64. A controller is typically provided to detect the temperature signals generated by sensors T1 and T2 and activate the pump 60 when T1 is sufficiently greater (ΔT) than T2 to indicate that energy transfer is warranted. The storage tank 64 includes a heat exchange coil (storage heat exchanger 62) of known construction and is insulated to contain the heat extracted from the roof space. Alternative embodiments may circulate excess heat to pools, spas or heating systems where appropriate.

FIG. 13 illustrates an alternative heat exchanger 80, which includes heat exchange tubes 22 and a plurality of brackets 56. In this heat exchanger 80, heat exchange tubes 22 are suspended in the path of air leaving roof ridge vent opening and the side extensions of the brackets are attached to the roof structure along either side of the opening. This heat exchanger 80 is compatible with other forms of ridge vent and can be installed independent of the ridge vent.

In the embodiments described above, it will be recognized that individual elements and/or features thereof are not necessarily limited to a particular embodiment but, where applicable, are interchangeable and can be used in any selected embodiment even though such may not be specifically shown.

Spatially orienting terms such as above, below, upper, lower, inner, outer, inwardly, outwardly, vertical, horizontal and the like when used herein refer to the positions of the respective elements shown on the accompanying drawing figures and the present invention is not necessarily limited to such positions.

It is also to be understood that the following claims are intended to cover all the generic and specific features of the disclosed embodiments and all statements of the scope of the embodiments which might be said to fall within the words of the claims. 

1. An energy recovery assembly for attachment to a roof of a structure having an interior air space beneath the roof and a vent opening through the roof communicating with the interior air space to permit air within the interior space to exit the interior space through the vent opening by convection, said heat recovery assembly comprising: an elongated flexible support, said support having a central portion between lateral side portions, said central portion being configured to laterally span said vent opening with said side portions fixable to the roof on opposite sides of the vent opening; a plurality of flexible heat exchange tubes secured to the central portion of said support, said heat exchange tubes arranged to permit air flowing through the vent opening to be in direct contact with said heat exchange tubes, wherein said energy recovery assembly is capable of being rolled and unrolled lengthwise and installed over the vent opening so that air flow through the vent opening transfers energy from the air to a working fluid circulating in said heat exchange tubes.
 2. The energy recovery assembly of claim 1, wherein said plurality of heat exchange tubes comprise a plurality of longitudinally extending tubes arranged in laterally spaced, substantially parallel relationship.
 3. The energy recovery assembly of claim 1, wherein said support web and said heat exchange tubes are constructed of plastic.
 4. The energy recovery assembly of claim 1, wherein at least one of said plurality of heat exchange tubes is connected to at least one other of said heat exchange tubes to form a fluid flow path approximately twice a length of said energy recovery assembly.
 5. The energy recovery assembly of claim 1, wherein said support has a top surface and a bottom surface and said plurality of heat exchange tubes are suspended beneath said bottom surface so that air flows between said support and said heat exchange tubes.
 6. The energy recovery assembly of claim 1, where in said support is a flexible air permeable web or mesh material that conforms to the roof when installed.
 7. The energy recovery assembly of claim 1, comprising receptacles attached to said support and configured to receive and hold said plurality of heat exchange tubes in a substantially fixed position with respect to said support.
 8. A heat exchange assembly for attachment to a structure defining an interior air space and including an elongated vent opening having a length and communicating with the interior air space to permit air within the interior space to exit the interior space through the vent opening by convection, said exchange assembly comprising: a plurality of continuous, flexible, open ended heat exchange tubes of indeterminate length; one or more supports, each including a central section between a pair of outer sections, said heat exchange tubes engaged with the central section of said supports at predetermined intervals along the length of said heat exchange tubes to maintain said heat exchange spaced from each other across said central section to permit air flow between said heat exchange tubes; and a plurality of connectors securable to the open ends of at least two of said heat exchange tubes to define a fluid flow path having a length at least twice the length of said elongated vent, wherein said heat exchange assembly is capable of being rolled and unrolled lengthwise and installed with said outer portions engaged to said structure on laterally opposite sides of said elongated vent to suspend said heat exchange tubes in direct contact with air flow exiting said interior air space.
 9. The heat exchange assembly of claim 8, wherein said plurality of heat exchange tubes are substantially parallel and substantially equally spaced across said central section.
 10. The heat exchange assembly of claim 8, wherein said support and said heat exchange tubes are constructed of plastic.
 11. The heat exchange assembly of claim 8, wherein said one or more supports comprise a single, longitudinally extending, air permeable mesh or web.
 12. The heat exchange assembly of claim 8, wherein said supports are positionable in a shape that conforms to the shape of a structure adjacent a vent in which the outer portions are disposed at dihedral angle relative to one another.
 13. An integrated roof ridge vent and heat exchange assembly for attachment to a roof of a structure having an interior air space beneath the roof and a vent opening through the roof communicating with the interior air space to permit air within the interior space to exit the interior space through the vent opening by convection, said heat recovery assembly comprising: an elongated flexible support of indeterminate length having a top surface and a bottom surface, said support having a central portion between a pair of lateral side portions configured to permit air flow therethrough, said lateral side portions having a thickness greater than said central portion; and a plurality of flexible heat exchange tubes extending the indeterminate length of said elongated flexible support and secured adjacent the bottom surface of said central portion in spaced apart relationship to each other and spaced from said bottom surface to permit air flowing through the vent opening to flow around said heat exchange tubes, wherein said integrated roof ridge vent and heat exchange assembly is capable of being rolled and unrolled lengthwise and installed spanning the vent opening so that air exiting the interior air space must flow past the heat exchange tubes.
 14. The integrated roof ridge vent and heat exchange assembly of claim 13, wherein said integrated roof ridge vent and heat exchange assembly is supplied as a continuous spiral roll.
 15. The integrated roof ridge vent and heat exchange assembly of claim 13, wherein said lateral side portions have a convoluted shape which defines open spaces to permit air flow between said top and bottom surfaces in a direction laterally away from said central portion.
 16. The integrated roof ridge vent and heat exchange assembly of claim 13, wherein said lateral side portions include an air permeable filter media which is secured to at least an outer lateral edge of said support to resist weather and insect penetration between said top and bottom surfaces.
 17. An energy recovery system adapted for use on a structure with a roof having an interior air space beneath the roof and a vent opening through the roof communicating with the interior air space to permit air within the interior space to exit the interior space through the vent opening by convection, said heat recovery system comprising: a first heat exchange assembly comprising: an elongated support, said support having a central portion and lateral side portions, said central portion being configured to laterally span said vent opening with said side portions fixed to the roof on opposite sides of the vent opening; a plurality of heat exchange tubes secured to the central portion of said support, said heat exchange tubes arranged to permit air flowing through the vent opening to be in direct contact with said heat exchange tubes, wherein said energy recovery assembly is installed over the vent opening so that air flow through the vent opening transfers energy from the air to a working fluid circulating in said heat exchange tubes; a first temperature sensor arranged in said air space to detect a temperature of the air in said air space and produce a first temperature signal corresponding to the temperature of the air in said air space; a fluid delivery loop defining a fluid flow path for a working fluid and including a circulation pump, said fluid delivery loop in fluid communication with said plurality of heat exchange tubes; a second heat exchange assembly in fluid communication with said fluid delivery loop and arranged to transfer heat energy from said working fluid to a storage medium; a second temperature sensor arranged to detect the temperature of said storage medium and generate a second temperature signal corresponding to the temperature of said storage medium; and a controller arranged to compare said first and second temperature signals and activate said circulation pump when said first temperature exceeds said second temperature by a predetermined temperature differential ΔT. 